title: Real-time temperature control system based on the finite element method for liver radiofrequency ablation: effect of the time interval on control.
abstract: Radiofrequency (RF) ablation is increasingly being used to treat liver cancer because it is minimally invasive. However, it is difficult for operators to control the size of the coagulation zones precisely, because no method has been established to form an adequate and suitable ablation area. To overcome this limitation, we propose a new system that can control the coagulation zone size. The system operates as follows: 1) the liver temperature is estimated using a temperature-distribution simulator to reduce invasiveness; 2) the output power of the RF generator is controlled automatically according to the liver temperature. To use this system in real time, both the time taken to calculate the temperature in the simulation and the control accuracy are important. We therefore investigated the relationship between the time interval required to change the output voltage and temperature control stability in RF ablation. The results revealed that the proposed method can control the temperature at a point away from the electrode needle to obtain the desired ablation size. It was also shown to be necessary to reduce the time interval when small tumors are cauterized to avoid excessive treatment. In contrast, such high frequency feedback control is not required when large tumors are cauterized.
authors.forename: Yosuke
authors.initials: Y
authors.lastname: Isobe
authors.forename: Hiroki
authors.initials: H
authors.lastname: Watanabe
authors.forename: Nozomu
authors.initials: N
authors.lastname: Yamazaki
authors.forename: XiaoWei
authors.initials: X
authors.lastname: Lu
authors.forename: Yo
authors.initials: Y
authors.lastname: Kobayashi
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Miyashita
authors.forename: Makoto
authors.initials: M
authors.lastname: Hashizume
authors.forename: Masakatsu G
authors.initials: MG
authors.lastname: Fujie
mesh_terms: D000465:Algorithms; D001831:Body Temperature; D017115:Catheter Ablation / Q000295:instrumentation* / Q000379:methods; D003198:Computer Simulation; D003199:Computer Systems; D004553:Electric Conductivity; D004566:Electrodes; D004867:Equipment Design; D005246:Feedback; D017143:Fuzzy Logic; D006801:Humans; D008099:Liver / Q000473:pathology; D008113:Liver Neoplasms / Q000628:therapy*; D011846:Radio Waves; D015203:Reproducibility of Results; D013696:Temperature